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1

6 Needs for rumen motility

1. Inoculate ingest with bacteria and protozoa

2. Mix saliva and ingesta to buffer acids produced by VFAs

3. Elimination of gas produced by bacteria

4. Prevent local accumulation of VFA at site of production

5. Assist VFA absorption through rumen wall

6. Prevent impaction by moving small particles into the lower GIT (omasum, abomasum and beyond)

2

Does the rumen have an intrinsic pacemaker?

No

3

If the rumen does not have intrinsic pacemaker, how does it have motility?

Innervated by Vagal Nerve

- multiple branches innervate different regions

 

4

Which contraction is the vagal nerve responsible for in the rumen?

primary and secondary

5

What does the vagal nerve affect in the motility of the rumen?

Frequency

Aplitude

Duration of motility

6

What does the vagal nerve fire based upon?

Activity in the bilateral gastric centers of the medulla

7

What type of autonomic response does the vagal nerve transmit to the rumen?

Parasympathetic

8

Other than the vagal nerve innervation, what is another innervation of the rumen?

Splanchnic motor nerves - sympathetic

- inhibit motility

9

3 Stimulatory inputs to gastric centres

1. Buccal mechanoreceptors (eating & chewing)

2. Tension receptors (high & low)

3. Epithelial (mucosal) receptors

10

Affects of tension receptors

Low tension receptors - increase motility

High tension receptors - stop motility

11

5 inhibitory inputs to gastric centers

1. High threshold tension receptors in reticulum and rumen

2. Tension receptors in abomasum

3. Epithelial receptors in rumen (pH)

4. Pain

5. Drugs (alpha-2 agonsits)

12

What do tension receptors in rumen cause?

Both increase and decrease rumen motility

13

2 type of epithelial Receptors

Mechanical

Chemical

14

What will acid in abomasum do?

Causes stimulatory signals to increase rumen motility

15

Explain the primary cycle of rumen motility

Major mixing contraction of ruminoreticulum

Last about 20 secs

Series of events

- Double contraction of reticulum

- Contraction of dorsal rumen sac (cranial to caudal)

- Contraction of ventral rumen sac (crainal to caudal and then caudal to cranial)

Occurs approx once/min

LOUD

16

What does frequency of primary cycle depend upon?

Eating: 35-45 secs

Resting: 60-90secs

Ruminating: 45-60 secs

17

How do we measure rumen motility through the fistula?

3 Catheters (attached to pressure transducer)

- One into the reticulum

- One under the mat in the dorsal sac

- One in the ventral sac

Connect to polygraph to measure pressure changes